I think most of the stuff you asked about ant be changed. as for afterburner, Gun position, heat blur etc I don't know. I have a theory you might can try though. If you make an aircraft flyable in the meinit XML file, you always get the Mig-29A cockpit or Mig-29S. Im not sure. But what if you replace the Mig-29 cockpit files witht he ones from the F15?. if that works you will have the animations of the F15 correct, the afterburner correct, heat blur correct, weapons correct etc. Though i dont know if you will be able to give the F18 a custom view point setup. might be possible to add some lines in the server.lua file to make that happen. Hope you can sort some stuff out, but by replacing the F15 model with the F18 one, you wont be able to change the problems you listed.
BW
Shaggy